Various types of waste material shredder are in use at the present time. These are used primarily for shredding documents in order to destroy the information content therein. However various other materials may be subjected to shredding, such as for example computer punch cards, printed circuit substrates, etc. Such waste material shredder can be broadly divided into two types, i.e. strip type shredders and cross-cut shredders. The strip type shredders act to cut sheets of waste material into elongated longitudinal strips, by a shearing action, while the cross-cut shredders cut the sheets of waste material into small chips, or very short strips. From the aspect of maximum destruction of any information contained in the waste material, and for minimizing the volume of the shredded output material, the cross-cut type of shredder is preferable. However a major problem which has arisen with prior art types of cross-cut shredder is that the shredded chips produced by the shredder tend to gradually accumulate within the mechanism, over a period of time, and to eventually cause the mechanism to be jammed, so that it becomes necessary for the user to periodically clear out such blockages from the shredder. This is extremely inconvenient, and is a major disadvantage of prior art cross-cut shredders by comparison with the mechanically simple strip type shredders.
More specifically, a cross-cut shredder generally comprises a pair of rotating shafts with their axes of rotation parallel to one another, with sets of cutter disks fixedly mounted on each shaft, and mutually meshing. Spacer members are fixedly mounted between the cutter disks of each shaft, to maintain a fixed separation between the cutter disks, and teeth are formed on the peripheries of the cutter disks. When such a shredder is operated over a long period of time, the shredded chips which are produced by a cutting action of the teeth and shearing between the cutter disks are not entirely removed from the mechanism, and gradually accumulated between the spacer members. As time elapses, this accumulation will increase to such an extent that the cutter disks can no longer rotate, and so the chips must be cleared out by the user.
With a waste material shredder according to the present invention, a special configuration for the cutter disks is employed, whereby the shredded chips are completely removed from the cutter mechanism immediately after they are produced, so that the problem described above is entirely eliminated. Thus a waste material shredder according to the present invention presents substantial advantages over prior art shredders with respect to ease of maintenance and reliability of operation.